Cast Infuse with Vitality by paying its mana cost.
Holding priority, cast Naru Meha by paying its mana cost.
When Naru Meha enters, it triggers, copying Infuse with Vitality, with the copy targeting Naru Meha.
Resolve the copy of Infuse with Vitality.
Holding priority, activate Shilgengar by sacrificing Naru Meha.
When Naru Meha dies, it triggers, returning it from your graveyard to the battlefield.
Repeat from step 3.
Resolve all Shilgengar abilities from step 5.
This loop hinges on a clever recursive engine powered by Naru Meha, Master Wizard, whose entry trigger allows her to copy spells right on the stack. By targeting herself with the copy of Infuse with Vitality, Naru Meha grants herself the delayed trigger she needs to automatically return to the battlefield whenever she bites the dust. Meanwhile, Shilgengar, Sire of Famine stands ready to sacrifice her for a Blood token (and a small burst of life from Infuse with Vitality along the way), letting you cycle Naru Meha in and out of the graveyard indefinitely.